This invention relates generally to a bone screw and method for its use, and more specifically to a bone screw and method for joining the fractured sections of a phalanx or the like.
In the fixation of fractured bone sections, a supporting member is often implanted into the fractured sections to stabilize those sections until these sections have had an opportunity to mend. With the phalanges, that is the bones of the fingers and toes, the supporting structure often takes the form of a pin which is inserted through the fractured section. The phalanges are generally hollow tube-like structure of boning material and a hole is bored through the center of the tubes and a metallic pin is inserted into this hole to keep the fractured segments aligned. The use of a pin, however, does not force the fractured sections together, but merely keeps them aligned along a central axis. To force the fractured sections of the bone together, a screw is often inserted into the bone sections to draw them together as well as to maintain axial alignment.
Bone screws take many forms. In one form the bone screw takes a "nut and bolt" form in which the bolt is inserted through a hole through two bone sections and the sections are drawn together by a nut which is threaded onto the bolt with the nut external to the bone sections. Such a bone screw is not applicable, however, to fractures of the phalanges.
In another form, as illustrated in U.S. Pat. No. 4,059,102, the bone screw is form in which the lading and trailing end portions of the screw have different diameters as well as opposite handed threads. The use of such a bone screw requires the drilling of a fairly large sized pilot hole to accommodate the end of the screw having the larger diameter. the large pilot hole adds to the trauma of the injury and is therefore an impediment to rapid recovery. If the diameter of the large sized end portion is made small to minimize the necessary pilot hole, the smaller end is necessarily too small of a diameater to have good holding power within the generally hollow phalanx.
In another form of bone screw is illustrated, for example, in U.S. Pat. No. 4,175,555, the bone screw is provided with screw threads which are like handed on each end, but are of a different pitch on the opposite ends of the screw. The use of such a screw requires the insertion of the screw along its total length. That is, the entire length of the screw must be threaded through a first one of the fractured sections and then into the other fractured section. During the insertion of the screw through its entire length, first set of threads is traumatizing the interior of the bone sections and then the other set of screws of different pitch, is further traumatizing at least one of the sections.
In view of the foregoing difficulties of supporting instruments for use in aiding the healing of fractured bones, a need existed for an improved bone screw and method for its use which would securely hold the fractured sections of bone together during healing without adding an undue amount of trauma.
It is therefore an object of this invention to provide an improved bone screw for joining fractured sections of a phalanx.
It is another object of this invention to provide an improved method for joining fracture sections of a phalanx.
It is yet another object of this invention to provide an improved bone screw and method for its use in joining fractured bone sections which provides for compressibly holding the bone segments without traumatizing the injured bone.